Crows, ravens and jays are medium to large birds. The group includes the largest members of the perching birds. Many crows, ravens and jays have large wingspans. They have a robust body, strong feet and sturdy bills. Their nares (nasal openings) are fringed by bristle-like feathers known as rictal bristles. In temperate areas, most members of the group are partly or entirely black, blue, iridescent blue or iridescent purple. Some species, such as the magpies and jays, are more varied in colour. They might have plumage with a mixture of black, white, grey and blue markings.
Members of this group of birds are thought to be highly intelligent, not just among birds but among all animals. Crows and rooks have demonstrated tool making abilities while European magpies have exibited self-awareness in mirror tests.
Many members of the crow family establish and protect territories either during the breeding season or throughout the year. When threatened, some corvids can defend their offspring or territories aggressively and are known to attack large animals such as other birds, dogs or cats. Many species of corvids form social groups and hierarchies for foraging and breeding.
Many species of corvids have flourished in human environments. But while such species have enjoyed healthy populations, a few corvids have experienced declines. Examples of threatened members of the crow family include the Florida scrub jay, the Mariana crow and the New Zealand raven.
Crows and their relatives form strong pair bonds and in some species this association is life-long. In most species, nests are constructed in trees or on rock ledges. Nests are built using twigs, grass and other plant materials. Females lay between 3 and 10 eggs and young fledge after about 10 days.
The crows, ravens and jays are divided into about a dozen subgroups, some of which include New World jays, grey jays, azure-winged magpies, Holarctic magpies, Stresemann's bushcrow, piapiac, true crows, nutcrackers, Old World jays, Oriental magpies, treepies and choughs.